Flux composition for zinc base alloys

ABSTRACT

THE PRESENT INVENTION COMPRISES AN IMPROVED NON-FUMING, LOW MELTING FLUX COMPOSITION FOR USE IN MELTING ZINCC AND ZINC BASE ALLOYS CONSISTING ESSENTIALLY OF FROM ABOUT 48 TO ABOUT 60 WEIGHT PERCENT POTASSIUM CHLORIDE, THE BALANCE BEING ESSENTIALLY LITHIUM CHLORIDE.

"United States Patent O 3,823,013 Patented July 9, 1974 US. Cl. 7565 R Claims ABSTRACT OF THE DISCLOSURE The present invention comprises an improved non-fuming, low melting flux composition for use in melting zinc and zinc base alloysconsisting essentially of from about 48 to about 60 weight percent potassium chloride, the balance being essentially lithium chloride.

This application is a division of Ser. No. 669,680, filed Sept. 22, 1967, and now abandoned.

Conventional fluxes for melting zinc and zinc base alloys usually contain zinc chloride (ZnCl ammonium chloride (NH Cl) or the double salt-zinc ammonium chloride. However, when the zinc melt contains reactive alloying elements such as, e.g., lithium, calcium, magnesium, or aluminum, such conventional fluxes are generally unsuitable because the reactive elements oxidize out of the zinc melt through reaction with the ZnCl or NH CI of the flux. For example, a ZnCl flux could not be used in melting the ASTM designated AC41A zinc base alloy containing 4 percent aluminum, 1 percent copper, and 0.04 percent magnesium, the balance being essentially zinc, because the ZnCl would remove at least a portion of the magnesium from the melt to form magnesium chloride (MgCl thereby tending to dilute the alloy with respect to its reactive alloying constituents.

Furthermore, conventional fluxes have a tendency to fume or vaporize when added to molten zinc and zinc alloys. This is particularly so with respect to a flux containing NH Cl which sublimes at about 335 C. Accordingly, it would be very desirable to obtain a flux composition suitable for melting zinc and zinc alloys containing magnesium, calcium, lithium, and aluminum which melts below the liquidus temperature of zinc (about 419 C.) but does not vaporize like the conventional flux composition. 1

A primary object of the present invention is to provide a low melting, non-fuming flux composition which is suitable for melting zinc and zinc base alloy containing reactive alloying elements.

A further object is to provide a low melting, non-fuming flux composition of potassium chloride and lithium chloride.

In accordance with the present invention the above and other objects and advantages are obtained in a novel flux composition consisting essentially by weight of from about 48 to about 60 percent potassium chloride, the balance being essentially lithium chloride, the flux being characterized as low melting and essentially non-fuming.

A preferred embodiment of the present invention comprises a flux composition consisting essentially of about 57 weight percent potassium chloride, the balance being essentially lithium chloride.

'While flux compositions within the present invention are particularly useful in melting zinc and zinc alloys having, e.g., magnesium, calcium, lithium or aluminum alloying substituents the flux composition can be used essentially in any operation where any molten zinc alloy is subject to oxidation.

The fiux composition of the present invention employs the advantage of liquidus temperature below about 419 C., the liquidus temperature of zinc. This permits the flux composition to melt and cover the zinc or zinc base alloy before the metal has liquified thereby reducing the opportunity for oxidation. Furthermore, since the oxide formed on the surface of an unprotected molten zinc alloy melt is soluble in the flux composition of the present invention, the present KCl-LiCl flux composition not only prevents further oxidation but also removes any oxide formed prior to the application of the flux. Accordingly, not only does the present flux composition avoid dilution of the alloy in a method of melting, but it also avoids oxide formations on the melt during the melting opera- 7 tion.

In preparing the flux compositions of the present invention, conventional fusing and grinding techniques, as practiced by those skilled in the art of flux preparation, may be employed, using commercially available compound constituents containing the normal amounts and types of impurities.

The following examples are representative of the novel flux compositions of the present invention and their use and are not intended to be construed as limiting the invention thereto.

EXAMPLE 1 A flux composed of about 57 Weight percent KCl and about 43 weight percent LiCl was prepared and applied to a melt of an alloy having a nominal composition of about 4 Weight percent aluminum, about 0.04 weight percent magnesium, the balance being essentially zinc. The alloy was melted in a carbon graphite crucible and covered with enough flux to provide a layer about inch thick on the surface of the metal. The metal was further heated to about 815 C. There was no evidence of oxidation of the melt or vaporization of the melt or of the flux composition even though this temperature is close to the boiling point of zinc (907 C.).

EXAMPLE 2 The procedure of Example 1 was repeated using a zinc 'melt having a nominal composition of about 0.25 weight percent aluminum, about 0.45 weight percent lithium, the balance being essentially zinc. Again there was no evidence of oxidation of the melt or vaporization of the melt or of flux composition.

EXAMPLE 3 A flux composed of about 50 weight percent KCl and about 50 weight percent LiCl may be prepared and ap plied to a Zinc melt having a nominal composition of about 4 weight percent aluminum, about 0.04 weight percent magnesium, the balance being essentially zinc. The melt may be further heated to about 800 C. If such procedure is carried out, there would be no evidence of oxidation of the melt or vaporization of the melt or of the flux composition.

The present invention may be modified or changed without departing from the spirit or scope thereof and it is understood that the invention is only limited as defined in the appended claims.

I claim:

1. A method of avoiding dilution of alloying constituents in melting a zinc base alloy containing reactive alloying constituents selected from the group consisting of calcium, lithium, magnesium, or aluminum, comprising: providing a flux composition consisting essentially of from about 48 to about 60 weight percent potassium chloride, the balance of the composition being essentially lithium chloride, and melting said zinc base alloy under an essentially continuous layer of said flux composition, thereby avoiding detrimental loss of said reactive alloy constituents during melting of the zinc base alloy.

2. The method of Claim 1 wherein the flux consists essentially of about 57 weight percent potassium chloride and the balance being essentially lithium chloride.

3. The method of Claim 1 wherein the zinc base alloy contains at least about 95 weight percent zinc.

4. The method of Claim 2 wherein the zinc base alloy contains at least about 95 weight percent zinc.

5. The method of Claim 1 wherein the flux melts at a temperature below about the liquidus temperature of ZlIlC.

6. The method of Claim 3 wherein the flux melts at a temperature below about the liquidus temperature of Zinc.

7. The method of Claim 1 wherein the flux melts at a temperature below about 419 C.

8. The method of claim 3 wherein the flux melts at a temperature below about 419 C.

9. The method of Claim 8 wherein the zinc base alloy contains aluminum and magnesium.

10. The method of Claim 5 wherein the zinc base alloy contains aluminum and magnesium.

References Cited UNITED STATES PATENTS 3,254,993 6/1966 Urban 75-135 2,817,895 12/1957 Chill 14826 i 4 3,512,959 5/1970 Joseph -94 3,145,097 I 8/1964 Derham 75-86 2,844,462 7/ 1958 Wyatt 75-86 3,171,735 2/1965 Gray 75-88 2,131,549 9/1938 iBerlin 75-93 3,153,602 10/ 1964 Duckett 75-94 3,160,531 12/1964 Spindler 136-153 2,701,194 2/ 1955 Deterding 75-94 2,472,025 5/ 1949 Peake 75-94 2,507,346 5/1950 Miller 148-26 2,865,798 12/ 1958 Hindson 148-26 3,414,407 12/1968 Jager 75-141 2,550,709 5/1951 Moe 148-26 2,569,097 9/ 1951 Grange 148-26 2,604,394 7/1952 Emley 148-26 FOREIGN PATENTS 979,583 1/ 1965 United Kingdom 75-10 L. DEWAYNE RUTLEDGE, Primary Examiner P. D. ROSENBERG, Assistant Examiner U.S. Cl. X.R. 75-86, 94 

